1. Field of the Invention
This invention relates to a folding insert which is used in forming an envelope-like jacket for a magnetic cartridge.
2. Description of the Prior Art
In recent years, a magnetic cartridge with a magnetic disk on which voice signals, video signals, data signals, etc. are recorded has been enclosed in an envelope-shaped jacket during storage and use. A magnetic cartridge of this type is inserted in a floppy disk device of a computer while the magnetic disk is enclosed in a jacket and the recorded information is reproduced by rotating the magnetic disk and by causing a reproduction head to contact a track thereon. Such a magnetic cartridge is described below with reference to FIG. 1.
A magnetic cartridge 1 comprises a magnetic disk 2 and a jacket 5 in which the magnetic disk is enclosed. The magnetic disk 2 is made of film having moderate flexibility, such as polyester resin, and is cut in the desired circular shape and an engaging hole 3 is provided at the center thereof. Various signals are recorded on a track 4 constituted by a magnetic layer coated on both surfaces thereof. The jacket 5 is made of thermosetting resin, such as vinyl chloride, and is a substantially square-envelope. A circular opening 6 slightly larger than the engaging hole 3 is bored at the central part of the jacket 5. A detecting hole 7 for the point of the start of reproduction and a slot 8 through which a reproduction head makes contact with the track 4 are provided on opposite sides of the circular opening 6. A ruled piece of paper 9 is stuck to the upper corner of the jacket. As shown in FIG. 2, the jacket is made of a rectangular sheet of material 10 which is folded in two. This jacket material 10 is covered with a nonwoven liner 11 over almost all the surface of the one side which becomes the inside of the jacket. The circular opening 6, the detecting hole 7 and the slot 8 are provided at the designated positions of the right half portion 12 and the left half portion 13. Flaps 14, 15 and 16 of small width are provided at the three sides of the left half portion 13.
This jacket material is fed onto a table of a jacket forming device (to be described later). The left half portion 13 of the jacket material is pressed by a folding insert (to be described later) and a folding bar (not shown in the drawings) is placed in tight contact with the underside of a center line 17 of the jacket material. By the revolution of the folding bar, the right half portion 12 is bent 180.degree. and is placed upon the folding insert. A heater bar (not shown in the drawings) is applied to the folded corner to form it in a sideward facing U shape. Then, flaps 14, and 15 at the two sides of the left half portion are bent 180.degree. by another folding bar, while the folding insert is still on the jacket material, and are placed on the side edges of the right half portion and the folded corners of the flaps are formed in a sideward facing U shape by another heater bar. Two portions 18 at both end portions of each flap are fused by ultrasonic waves or the like and the jacket material is pulled off the folding insert. Next, the ruled paper 9 is stuck to an upper corner of the left half portion 13 which becomes the front side and thus an envelope-shape jacket having a fixed opening is produced. The magnetic disk 2 is inserted in this jacket, the flap 16 is bent 180.degree., the folded corner is heated by the heater bar for formation of a sideward facing U shape and finally two portions 19 at both end portions of the flap 16 are fused. Thus, the magnetic cartridge is finished. It is possible to punch the circular opening 6, the detecting hole 7 and the slot 8 on both portions after the jacket 5 has been produced.
Since this magnetic cartridge is inserted in a floppy disk device of a computer with the magnetic disk 2 enclosed in the jacket 5, it has such advantages that the magnetic layer of the magnetic disk is free from being coated with dust and is kept clean by the liner 11 while the magnetic disk is turning. On the contrary, however, high precision is required for the external form and dimensions of the jacket.
Conventionally, a folding insert which is a simple flat plate is used for forming the jacket but such a folding insert cannot bend the flap of jacket material more than 180.degree. and therefore when a bent flap is fused at two portions, its intermediate portion is liable to rise, with resultant formation of a gap, or the back surface of a jacket is raised due to flyback of the flap, causing swelling at its inner part. Such jackets which have a poor external shape and dimensions are difficult to insert in a floppy disk device. Even if the jacket is inserted, the magnetic disk will not rotate smoothly and consequently reproduction of the recorded material will be inaccurate and cleaning of the magnetic coating by the liner cannot be achieved.